Effects of intake level on metabolic response to estrogenic growth promoters in beef steers.
Effects of diethylstilbestrol (DES, 10 mg/d orally, Trial 1) or Synovex-S (SYN, 220 mg ear implant, Trial 2) on gain and N balance (g/d) were determined in steers that consumed 1.3, 2.7, 4.4 and 7.4 kg DM/d (Trial 1) and 1.3, 2.9, 4.3 and 6.6 kg DM/d (Trial 2). Each trial was a replicated 4 x 4 Latin square with four pairs of steers per trial (BW:322 kg, Trial 1; 278 kg Trial 2) and a control and growth promoter steer in each pair. Steers were fed a pelleted 75% concentrate diet containing 16.7% (DM basis). Each period consisted of 1 wk of intake adaptation, 5 wk of feeding and 1 wk in metabolism crates (2-d adjustment and 5-d collection). Steers were switched among DMI but not among promoter treatments. Intercept and slope, respectively, for the regression of BW gain (kg/d) on DMI (kg/d) were -.66 and .276 for control vs -.84 and .328 for DES steers and -.69 and .276 for control vs -.89 and .356 for SYN steers. Similar regression values for N balance (g/d) on DMI (kg/d) were -10.3 and 6.91 for control vs -17.2 and 9.10 for DES steers and -4.5 and 4.67 for control vs -7.6 and 5.85 for SYN steers. Across trials, slopes differed from zero (P less than .01), and promoter slopes differed from controls for gain (P less than .01) and N balance (P less than .10). During an extra period at the end of each trial, all steers were fed the high intake level for 6 wk, followed by N balance determinations the last 3 d of a 7-d fast.(ABSTRACT TRUNCATED AT 250 WORDS)
Rumsey
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U.S. Department of Agriculture, Beltsville, MD 20705.
Hammond
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D000821:Animal Feed; D000818:Animals; D002417:Cattle / Q000254:growth & development / Q000378:metabolism*; D004044:Dietary Proteins / Q000378:metabolism; D004054:Diethylstilbestrol / Q000008:administration & dosage / Q000494:pharmacology*; D004063:Digestion / Q000187:drug effects; D004338:Drug Combinations; D004958:Estradiol / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D008297:Male; D009584:Nitrogen / Q000378:metabolism; D011374:Progesterone / Q000008:administration & dosage / Q000494:pharmacology*; D012044:Regression Analysis; D015430:Weight Gain / Q000187:drug effects
D004044:Dietary Proteins; D004338:Drug Combinations; D011374:Progesterone; D004958:Estradiol; D004054:Diethylstilbestrol; C025370:estradiol benzoate, progesterone drug combination; D009584:Nitrogen